Thermoelectric Comfort Control System for Motor Vehicle

ABSTRACT

A temperature control apparatus for an interior of a motor vehicle having a temperature control loop circulating a heat-exchange fluid to a drivetrain component. A thermoelectric heat-pump (Peltier device) is disposed in the vehicle to heat or cool the desired area, and a fluid comfort control loop exchanges heat with the thermoelectric heat-pump and with the drivetrain temperature control loop, increasing the net amount of heating or cooling that can be delivered to the desired location by the thermoelectric heat-pump. The comfort control loop may branch from the drivetrain loop and carry a portion of the heat-exchange fluid carried in the drivetrain loop. Alternatively, the comfort control loop may carry a second heat-exchange fluid that remains separate from the heat-exchange fluid of the drivetrain loop and exchanges heat therewith in a heat exchanger.

TECHNICAL FIELD

The present invention relates to a comfort control system for a vehiclethat includes a thermoelectric heat pump (Peltier device) having a fluidtemperature control loop, and specifically to such a system in whichenergy efficiency is improved by the exchange of heat energy between thetemperature control loop and a second fluid temperature control loopthat controls the temperature of a drivetrain component.

BACKGROUND

Electric powered vehicles (including hybrid-electric vehicles, fuel cellvehicles, plug-in electric vehicles, etc.) have one or more drivetraincomponents that should be maintained within a desired operatingtemperature range for optimum performance. Examples of such drivetraincomponents are high-voltage batteries, electric machines (motors,generators, and/or combined devices), and transmissions. Under someoperating conditions, a temperature control system is necessary to cooland/or heat the components to maintain them within the desiredtemperature range.

It is known to provide a temperature control system in which a fluid(usually a liquid) is circulated to, through, or around the drivetraincomponent where the fluid removes (or adds) heat energy, and through aheat exchanger to reject (or absorb) heat energy to some other medium,usually ambient air. In this context, the term “heat exchanger” refersto any apparatus that may achieve the desired result of adding and/orremoving heat to/from the fluid circulating in the control system. Thisheat exchange function may be performed by apparatus such as afluid/fluid heat exchanger, a refrigerant-cycle heat pump, and athermoelectric heat pump (also known as a Peltier device).

Thermoelectric heat pumps are currently used in some automotive vehiclesto cool and/or heat a storage compartment in order to store food ordrinks at a desired temperature. It is also known to use thermoelectricheat pumps to heat and/or cool seats in the vehicle interior. In such“air conditioned seats,” the seating surface which contacts the seatoccupant is typically perforated and a fan circulates air over the coldside of the Peltier cooler and blows the cooled or heated air out of theperforations in the seat skin.

It has also been proposed to integrate a liquid heat exchanger with athermoelectric heat pump. In this concept, a liquid working fluid passesthrough the heat pump. In heating mode, heat is pumped from the workingfluid through the thermoelectric device into the passenger comfort air.In cooling mode, heat is rejected from the air into the liquid workingfluid.

SUMMARY

The object of the invention is to improve the overall energy efficiencyof a motor vehicle, in particular an electric vehicle, by reducing oreliminating the need to use electric power to run a conventional heateror air conditioning unit to achieve a comfortable cabin temperature.

According to a feature disclosed herein, an interior temperature controlapparatus for a motor vehicle having a temperature control loop carryinga heat-exchange fluid to a drivetrain component comprises athermoelectric heat-pump disposed in the vehicle, and a comfort controlloop exchanges heat with the thermoelectric heat-pump and with thedrivetrain temperature control loop. This increases the net amount ofheating or cooling that can be delivered to the desired location by thethermoelectric heat-pump, thereby reducing the amount of electricalpower that may otherwise be needed to run the climate control system.

According to another feature disclosed herein, the comfort control loopbranches from the drivetrain loop and carries a portion of theheat-exchange fluid carried in the drivetrain loop.

According to another feature disclosed herein, the comfort control loopcarries a second heat-exchange fluid that exchanges heat with theheat-exchange fluid of the drivetrain loop.

According to another feature disclosed herein, an apparatus forpassenger comfort control in a motor vehicle comprises a drivetraincomponent, a temperature control loop circulating a heat-exchange fluidto the drivetrain component, a thermoelectric heat-pump disposed in apassenger compartment of the vehicle, and a comfort control loopbranching from the temperature control loop and carrying a portion ofthe heat-exchange fluid to the thermoelectric heat-pump.

According to another feature disclosed herein, the passenger comfortcontrol apparatus further comprises a HVAC system circulating airthrough the passenger compartment, and an electronic control unitcontrolling the HVAC system and the thermoelectric heat-pump.Integrating the control of the thermoelectric heat pump with the HVACsystem achieves optimum energy management, thereby minimizing energyusage while maintaining a comfortable passenger environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic system diagram of a thermoelectric comfort controlsystem according to a first disclosed embodiment;

FIG. 2A is a schematic depiction of a thermoelectric heat pump withfluid a heat exchange fluid loop;

FIG. 2B is a schematic depiction of a Peltier element of the type usedin a thermoelectric heat pump; and

FIG. 3 is schematic system diagram of second embodiment of athermoelectric comfort control system.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring to FIG. 1, a thermoelectric comfort control system for avehicle includes one or more thermoelectric heat pumps 10 located in,on, or adjacent to a passenger compartment of a vehicle. In the depictedembodiment, thermoelectric heat pumps (TEHP) are located inside apassenger seat 12, one in the seat bottom and one in the seat back.TEHPs may be provided at other locations within a passenger cabin whereheating and/or cooling is required, such as beneath a seat, adjacent afoot-well area, behind a body trim panel (e.g., headliner or door trim),or behind the instrument panel. Further, TEHPs may be located within oradjacent to a storage compartment in order to heat and/or cool thestorage compartment as may be required, for example, to store food ordrinks at a desired temperature.

TEHPs as described herein operate on the well-known Peltier effect inwhich a DC electric voltage is applied across pairs of n-type and p-typethermo elements to cause an electron flow and resulting heat transferfrom a “cold side” to a “hot side” of the elements. Reversing thepolarity of the DC voltage reverses the flow of electrons and results ina switching of the hot side and cool side. Accordingly, a single TEHPmay be used either as a heating device or a cooling device by simplyapplying the appropriate voltage polarity.

The following description primarily discusses the situation where TEHPs10 are used to cool the vehicle interior. This should, however, not beconstrued to limit the scope of the present invention since, as notedabove, TEHPs 10 may easily be operated to heat the vehicle interior ifdesired.

A comfort control loop 14 circulates a heat exchange fluid through TEHPs10. Comfort control loop 14 may comprise hollow pipes or tubes thatenter TEHPs and pass across one side of the Peltier devices to allow anexchange of heat energy between the fluid and the Peltier device, andexit the TEHP. In the embodiment depicted in FIG. 1, comfort controlloop 14 branches off from a drivetrain temperature control loop 16 andcarries a portion of the heat exchange fluid circulating through thedrivetrain temperature control loop.

The amount or portion of heat exchange fluid that is diverted from thedrivetrain temperature control loop 16 to circulate through comfortcontrol loop 14 may be regulated by one or more valves 18 that arepreferably controlled by an electronic control unit (ECU) 20, theoperation of which will be further described below. A pump 19 may beprovided to provide additional control over the amount and direction ofthe flow of fluid through comfort control loop 14.

Drivetrain temperature control loop 16 exchanges heat energy with one ormore drivetrain components 22 and with a heat exchanger 24. In anelectrically powered vehicle, drivetrain components 22 may comprise oneor more components such as a high-voltage battery, electric motors,generators, and power electronics (such as DC/DC or AC/DC converters).Under most vehicle operating conditions, such drivetrain components willgenerate excess heat when operating, so that the heat exchange fluidcirculating in drivetrain temperature control loop 16 carries heat awayfrom the components. Heat exchanger 24 may comprise one or more of aconventional liquid-to-liquid or liquid-to-air exchanger, a heat pumpusing a fluid refrigerant cycle, or a thermoelectric (Peltier) heatpump. In any event, the objective of drivetrain temperature control loop16 and heat exchanger 24 is to heat or cool drivetrain component 22 asis necessary to maintain a desired operating temperature range.

ECU 20 may receive signals or inputs from a variety of sensors andcontrols. Examples of such sensors include: cabin temperature sensor(s)26; exterior temperature sensor(s) 28; and sensor(s) 32 monitoringconditions of drivetrain components 22, heat exchanger 24, or drivetraintemperature control loop 16. Inputs may be made by a vehicle occupantusing a climate control panel 30. Such inputs may include desiredtemperature, fan speed, direction of air flow, or simply “heat” or“cool.” ECU 20 controls the condition of valve(s) 18 and/or pump 19 toregulate the direction and/or flow rate of heat exchange fluid to TEHPs10. ECU 20 preferably also controls the electricvoltage/current/polarity applied to the Peltier elements within TEHPs10. By monitoring and/or controlling the basic parameters of thetemperature and volume flow rate of the heat exchange fluid travelingthrough comfort control loop 14 and the voltage and polarity of thecurrent applied to the Peltier devices and TEHPs 10, ECU 20 controls theamount or level of heating and/or cooling supplied to vehicle interiorand any occupants.

Heat transfer from/to TEHPs 10 may be enhanced by one or more fans orother air movement devices (not shown) integrated with or locatedadjacent to the TEHPs to circulate air over the occupant/cabin side ofthe Peltier device. ECU 20 may also control the on/off condition and/orthe speed of the fans.

ECU 20 may also control other vehicle comfort control systems, such asan HVAC system 36, and may have one or more automatic climate controloperating modes. HVAC system 36 comprises apparatus for circulatingheated, cooled, or otherwise conditioned air through the vehicleinterior, such as a conventional air conditioning system and/or vehicleheater. Alternatively ECU 20 may be connected with a separate controldevice (not shown) for HVAC system 36 so that the two systems mayoperate in a coordinated manner.

As shown schematically in FIG. 2A, a possible embodiment of a TEHP 10includes Peltier elements 50 arranged on opposite sides of a multi-tubeconduit 52. Conduit 52 is part of comfort control loop 14 and conductsheat exchange fluid in a direction into/out of the page. Fins 54 extendoutwardly from Peltier elements 50 in both directions (up and down, asviewed in FIG. 2A), and the entire structure is contained in an air flowhousing 56. A fan 48 (or other air movement device) is positioned toforce air (usually ambient air from the passenger cabin or otherinterior compartment of the vehicle) through air flow housing 56 andover fins 54. The air flow exits TEHP 10 and passes into the portion ofthe vehicle interior that is being warmed or cooled by the system.

FIG. 2B shows, again in schematic form, an example of a Peltier element50. Each Peltier element comprises a p-type element 50 a and an n-typeelement 50 b electrically connected with one another and with a DCvoltage source as shown. When the indicated polarity is applied, theside of element 50 in contact with conduit 52 (see FIG. 2A) becomes thehot side and the opposite side, in contact with fin 54, becomes the coldside.

On a warm day, when vehicle occupants are most likely to be using TEHPs10 in a cooling mode, heat energy from the hot side of the Peltierelements passes to the heat exchange fluid in the comfort control loop14 as it circulates through the TEHPs. Thus, the fluid carries heat outof the passenger compartment and travels to/through heat exchanger 24along with the rest of the heat exchange fluid circulating through thedrivetrain temperature control loop 16. Also on such a warm day,drivetrain components 22 will usually generate excess heat that must beremoved by the drivetrain loop 16 in order to maintain the drive traincomponents within the desired operating temperature range. So heatexchanger 24 will be operating in a mode to cool the fluid circulatingin drivetrain loop 16. If heat exchanger 24 is a heat pump (refrigerantcycle or Peltier), it will be operated in a cooling mode, which iscompatible with the need to cool the fluid reaching the heat exchangerfrom the comfort control loop 14.

Under colder ambient conditions, vehicle occupants are likely to beusing TEHPs 10 in a heating mode, in which heat exchange fluidcirculating though comfort control loop 14 passes over the cold side ofthe TEHPs. The fluid therefore exits TEHPs 10 cooler than when itentered and must gain heat energy before returning to the TEHPs. Underall but very cold ambient conditions, this need for heat energy will bemet by the excess heat generated by drivetrain components 22. Under verycold conditions, drivetrain components 22 may need to be warmed by thedrivetrain temperature control loop 16 in order to stay within thedesired operating temperature range. In this case, heat exchanger 24will operate in a mode to warm the fluid circulating in drivetrain loop16, and the branching comfort control loop 14.

The direction in which the fluid flows through comfort control loop 14may be controlled (using a bi-directional pump 19 or any otherappropriate means) as necessary to divert working fluid from powertrainloop 16 at the location best suited for operation of the system. Theflow direction may depend on many factors, such as ambient temperature,fluid temperatures, drivetrain component temperatures, commandedfunction of the TEHP, etc.

FIG. 3 shows a second embodiment of a thermoelectric heat pump comfortcontrol system in which heat is exchanged between the comfort controlloop 114 and the drivetrain temperature control loop in a mannerdifferent from the embodiment of FIG. 1. In this second embodiment,drivetrain components 122 are oil-cooled components such as, forexample, a mechanical transmission or an electric machine (generator,motor, or integrated motor/generator). The cooling oil is circulatedthrough a primary drivetrain loop 116 a to an oil-to-coolant heatexchanger 124 a by a pump 23.

A secondary drivetrain cooling loop 116 b contains a second heatexchange fluid that circulates through oil-to-coolant heat exchanger 124a and a second fluid-to-air heat exchanger 124 b. Comfort control loop114 also passes through the oil-to-coolant heat exchanger 124 a underpressure provided by a pump 38 controlled by ECU 20. The heat exchangefluid circulating in comfort control loop 114 remains physicallyseparate from both the primary and secondary drivetrain control loops116 a and 116 b and may exchange heat with either or both of the fluids(oil and/or coolant) carried in those loops, depending on the interiorconfiguration of oil-to-coolant heat exchanger 124 a. In this secondembodiment, as with the first embodiment of FIG. 1, the comfort controlloop exchanges heat with the drivetrain temperature control loop inorder to increase the amount of heat that it is possible to efficientlytransfer into (or out of) the desired portion of the vehicle cabin usingthermoelectric heat pumps.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

1. Apparatus for improving the energy efficiency of a motor vehiclehaving a drivetrain temperature control loop carrying a heat-exchangefluid to a drivetrain component, the apparatus comprising: athermoelectric heat-pump disposed in the vehicle ; and a comfort controlloop exchanging heat with the thermoelectric heat-pump and with thedrivetrain temperature control loop.
 2. The apparatus of claim 1 whereinthe comfort control loop branches from the drivetrain loop and carries aportion of the heat-exchange fluid.
 3. The apparatus of claim 2 whereinthe portion of the fluid carried by the comfort control loop isregulated by at least one valve.
 4. The apparatus of claim 3 wherein theat least one valve is controlled at least in part by an automaticclimate control system.
 5. The apparatus of claim 1 wherein the comfortcontrol loop carries a second heat-exchange fluid that exchanges heatwith the heat-exchange fluid of the drivetrain loop.
 6. The apparatus ofclaim 5 wherein the comfort control loop and the drivetrain loopexchange heat in a heat exchanger.
 7. The apparatus of claim 1 whereinthe drivetrain component is at least one of a battery, a fuel cell, anelectric motor, a power electronics unit, and a mechanical transmission.8. The apparatus of claim 1 wherein the thermoelectric heat-pump islocated in a passenger seat.
 9. The apparatus of claim 1 wherein thedrivetrain temperature control loop comprises a heat exchanger throughwhich the heat-exchange fluid flows.
 10. The apparatus of claim 9wherein the heat exchanger is a second thermoelectric heat-pump.
 11. Asystem for improving the energy efficiency of a motor vehiclecomprising: a drivetrain component; a temperature control loopcirculating a heat-exchange fluid to the drivetrain component; athermoelectric heat-pump disposed in a passenger compartment of thevehicle; and a comfort control loop branching from the temperaturecontrol loop and carrying a portion of the heat-exchange fluid to thethermoelectric heat-pump.
 12. The system of claim 11 wherein thedrivetrain component is at least one of a battery, a fuel cell, anelectric motor, a power electronics unit, and a mechanical transmission.13. The system of claim 11 wherein the portion of the fluid carried bythe comfort control loop is regulated by a valve.
 14. The system ofclaim 13 wherein the valve is controlled by an automatic climate controlsystem.
 15. The system of claim 11 wherein thermoelectric heat-pump islocated in a passenger seat.
 16. The system of claim 11 wherein thetemperature control loop comprises a heat exchanger through which theheat-exchange fluid flows.
 17. The system of claim 16 wherein the heatexchanger is a second thermoelectric heat-pump.
 18. Apparatus forimproving the energy efficiency of a motor vehicle comprising: adrivetrain component; a temperature control loop circulating aheat-exchange fluid to the drivetrain component and including adrivetrain heat exchanger; a thermoelectric heat-pump disposed in apassenger compartment of the vehicle; and a comfort control loopexchanging heat with the drivetrain temperature control loop and withthe thermoelectric heat-pump.
 19. The apparatus of claim 18 furthercomprising: a HVAC system circulating air through the passengercompartment; and an electronic control unit controlling the HVAC systemand the thermoelectric heat-pump.
 20. The apparatus of claim 18 whereinthe comfort control loop branches from the drivetrain temperaturecontrol loop and carries a portion of the heat-exchange fluid.